The Museum of HP Calculators

HP Forum Archive 15

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How valuable are upgraded HP48G's?
Message #1 Posted by Han on 14 Dec 2005, 7:12 a.m.

I have several HP48G calculators which I've upgraded to 256kB memory (and am thinking of adding in port2 in the near future). I did the upgrades without drilling, faceplate removal, or any cuts -- so they look as if they were never tampered with. No PCB was used either (I just stacked two SMD RAM chips on top of each other and placed them where the old 32kB chip used to be). Are the values of these calcs even less than that of a used HP48G because they've been opened up? Or would they be more valuable since they currently have 256kB of memory?

Re: How valuable are upgraded HP48G's?
Message #2 Posted by Namir on 14 Dec 2005, 12:28 p.m.,
in response to message #1 by Han

Sell it on eBay and see what the demand is!!!


Re: How valuable are upgraded HP48G's?
Message #3 Posted by tomc on 14 Dec 2005, 11:08 p.m.,
in response to message #2 by Namir


I agree; see what the demand is on ebay. I too intend to upgrade a 48 or two, but don't intend to sell them.

I would be curious if you would like to share some of the details of your opening process (is it the method we've seen on the web?).

Not to digress too much, but you might be interested to know that a HP38G has several unique features of interest to us 48 'hacks': 1. It appears to be able to accept a 128k RAM like the 48G. 2. It looks as if it will accept a DIP package 128k RAM. 3. There is another curious 16pin DIP pcb pattern - I intend to figure out what it is someday.

I believe one could drop a 48G ROM in this thing and get it to 'be' a 48G(+). Haven't tried it yet...

Perhaps others have already noticed these things, but I haven't seen it documented very well anywhere.

Regards, TomC

Re: How valuable are upgraded HP48G's?
Message #4 Posted by Han on 15 Dec 2005, 8:36 p.m.,
in response to message #3 by tomc

Hi Tom,

Well, the suggestion of placing the calculator on eBay sounds like the perfect way to find out. Though, I would rather not sell any of my HP48s =). I am merely curious what collectors think of modified calculators.

As for the method I used to open the HPs, I used a method that I figured out myself -- though it turns out someone else has also done it before. By using just a flat edge, you can open the HP without doing any cosmetic or even structural damage. And it's quite easy. Even when you put everything back together, the calculator feels just as solid as before because the rivets will still pop back into place.

I took many photos which I hope to put together to explain the entire process. I will have some time in January to make further upgrades (adding in port 2), and will put together a zip file containing all the photos and explanations. I've already designed a PCB board that will make use of SMD RAM chips as oppposed to the bulky DIP chips. I learned quite a bit about the HP48, and hope to share what I've found out. If you have any questions, I'd be more than happy to answer them to the best of my ability.


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